The design of a chemical entity that potently and selectively
binds
to a biological target of therapeutic relevance has dominated the
scene of drug discovery so far. However, recent findings suggest that
multitarget ligands may be endowed with superior efficacy and be less
prone to drug resistance. The Protein Data Bank (PDB) provides experimentally
validated structural information about targets and bound ligands.
Therefore, it represents a valuable source of information to help
identifying active sites, understanding pharmacophore requirements,
designing novel ligands, and inferring structure–activity relationships.
In this study, we performed a large-scale analysis of the PDB by integrating
different ligand-based and structure-based approaches, with the aim
of identifying promising target associations for polypharmacology
based on reported crystal structure information. First, the 2D and
3D similarity profiles of the crystallographic ligands were evaluated
using different ligand-based methods. Then, activity data of pairs
of similar ligands binding to different targets were inspected by
comparing structural information with bioactivity annotations reported
in the ChEMBL, BindingDB, BindingMOAD, and PDBbind databases. Afterward,
extensive docking screenings of ligands in the identified cross-targets
were made in order to validate and refine the ligand-based results.
Finally, the therapeutic relevance of the identified target combinations
for polypharmacology was evaluated from comparison with information
on therapeutic targets reported in the Therapeutic Target Database
(TTD). The results led to the identification of several target associations
with high therapeutic potential for polypharmacology.